Non-SELEX method for aptamer selection against β-casomorphin-7 peptide

The non-systematic evolution of ligands by the exponential enrichment (non-SELEX) method was used in the present study for the selection of beta-casomorphin-7 (BCM-7)-specific aptamers. These aptamers were tested to evaluate their ability to detect BCM-7 peptide in the human urine sample. The method did not employ aptamer amplification and counterselection as used in conventional SELEX but included a negative round of selection. The selection was performed in a single day, and after 5 rounds, a total of 16 numbers of aptamer were identified through Sanger sequencing. Newly selected aptamers named sequence ID no. 3 have performed better than other aptamers in detecting the BCM-7 peptide. Sequence ID no. 3 was also compared with previously selected aptamers through the SELEX method and its performance was found to be better than old aptamers. The sensing experiment was tried on different platforms from magnetic beads to the membrane. In each strategy, satisfactory results were obtained with aptamers that recognized BCM-7 spiked in a human urine sample at a very low amount. The non-SELEX method is an easy and time-saving process for aptamer selection. Selection of viable aptamers from a large pool of sequences for sensing experiments is a tedious job; however, an attempt has been made to select aptamers on the basis of In Silico (http://www.unafold.org/, https://bioinformatics.ramapo.edu/QGRS/index.php) information, observing DNA band intensity on agarose gel and colorimetric results obtained on magnetic beads and membrane. These aptamers have the potential in biosensor making for detecting BCM-7 peptide in urine samples of autistic patients.

Automated summary

The non-systematic evolution of ligands by the exponential enrichment (non-SELEX) method was used to select specific aptamers for detecting BCM-7 peptide in urine samples. The method did not involve aptamer amplification and counterselection, but included a negative selection round. After 5 rounds of selection, a total of 16 aptamers were identified, with sequence ID no. 3 performing the best in detecting BCM-7 peptide. The non-SELEX method is a time-saving process for aptamer selection. These aptamers have potential applications in biosensors for detecting BCM-7 peptide in urine samples of autistic patients.